1. Field of the Invention
The invention relates generally to the field of telemetry systems used for instruments disposed in a wellbore during the drilling thereof. More particularly, the invention relates to “wired” drill pipe power and telemetry communication systems.
2. Background Art
Wellbores are drilled through subsurface Earth formations for, among other purposes, extracting useful materials such as petroleum. Typically drilling techniques include disposing drilling tools such as a drill bit, drill collars, jars, stabilizers and other devices at the end of a number of segments (“joints”) of threadedly coupled pipe. The pipe is suspended and rotated at the surface by a drilling rig. Drilling fluid is pumped through an interior passage way in the pipe and is discharged at the bottom of the wellbore through nozzles or similar orifices in the drill bit to circulate drill cuttings out of the wellbore and to cool and lubricate the drill bit.
It is known in the art to include in the foregoing drilling tools a number of sensing devices, collectively known as “measurement while drilling” and “logging while drilling” instruments for the purpose of measuring such things as the direction and inclination of the drill bit, the temperature and pressure near the drill bit, as well as various physical parameters of the Earth formations penetrated by the wellbore. Measurements made by the foregoing instruments are typically stored in a recording device, such as a solid state memory, disposed in one or more of such instruments. Certain of the measurements are also transmitted to the surface by one or more telemetry devices, such as a mud-pulse telemetry device that modulates the flow of the drilling fluid to create signals in the mud flow.
The measurements made by the foregoing instruments can be quite valuable when transmitted to the surface during the drilling of a wellbore. For example, measurements of physical properties of the subsurface formations may indicate to the wellbore operator that particular subsurface formations are about to be penetrated. Where such penetration may require particular preparation, advance information may prevent expensive damage to the wellbore or other drilling hazards. Such measurements may also be made at a time when there is little mud invasion of the formation, making the measurements more accurate. Other examples of useful information transmitted to the surface may include measurements concerning motion of the drilling tools in the wellbore. Such measurements can indicate that the drilling tool assembly is undergoing destructive vibration, or is moving in a manner such that much of the energy supplied by the drilling rig is dissipated rather than being used to drill the subsurface formations.
The above described systems have at best been able to transmit signals to the surface at several bits per second. Obtaining information about the subsurface formations in sufficient detail and information concerning the drilling tool movement may require signal transmission rates several orders of magnitude greater than is possible conventional telemetry. Such requirement has been long recognized by the petroleum industry, and a number of different “wired” drill pipe systems have been proposed. See, for example, U.S. Pat. No. 4,806,115 issued to Chevalier, et al., and U.S. Pat. No. 4,095,865 issued to Dennison, et al. More recently, wired drill pipe including inductive couplers between joints of pipe has been proposed. See U.S. Pat. No. 6,670,880 issued to Hall, et al. Using electrical and/or optical conductors arranged with the drill pipe may enable transmission of signals at much higher rates than is possible using mud pulse telemetry.
Irrespective of the type of wired drill pipe system used, most drilling tool assemblies include devices such as described above including jars, drill collars, stabilizers, etc. Such devices are frequently disposed in the drilling tool assembly between the drill pipe and the lower part of the drilling tool assembly where the sensing devices referred to above are typically located. In order to provide signal communication using wired drill pipe across tools such as jars, drill collars, and stabilizers, it would be necessary to provide structures in such tools that are compatible with the particular type of wired drill pipe system used. Having wiring structures in the foregoing drilling tools is difficult and expensive, particularly because such drilling tools as subject to frequent repair to the threaded connectors at each longitudinal end.
There exists a need for a wired drill pipe system than can be used with ordinary drilling tools such as collard, jars, stabilizers and the like that do not have wiring structures therein.
It is also desirable to provide a “wired” connection between instruments in the wellbore and surface equipment, in order to provide a high-bandwidth communication channel between such instrument and surface equipment.